Field of the Invention
The present invention relates to an elevator system especially for high-rise multi-floor buildings where a passenger who wants to get to a floor in the top part has to change to an elevator that mainly serves the topmost floors only.
In very tall buildings, it is generally economically not possible to provide elevator shafts extending through the entire height of the building from the bottom floor to the top floor so that each elevator could serve all floors. For this reason, elevators are traditionally divided into different zones in the vertical direction, of which the lowest zone extends from the entrance floor, hereinafter called ground floor, to a floor at a given height, this zone being called low-rise zone, while the highest zone, called high-rise zone, extends from a given transfer floor, a so-called sky lobby floor to the topmost floors of the building. Between these zones, depending on the height of the building, there may be one or more intermediate zones, so-called mid-rise zones serving intermediate floors in the building from their respective transfer floors. The problem is generally that each zone is served by only one elevator in one elevator shaft, so it is necessary to provide for each zone and each elevator car a separate shaft extending from the ground floor of the building to the top floor of the zone. In addition, a machine room is generally provided above each elevator, which requires more space. Moreover, with increasing building height, there is the problem that it is difficult to provide a sufficient transport capacity especially to the higher floors, because in the highest shaft the traveling distance from the ground floor to the highest sky lobby is long. A further disadvantage is the highest shafts is the difficulty of compensation of long elevator ropes, which is not encountered in lower elevator shafts as the ropes are shorter.
In tall buildings, however, a single elevator aggregate with zone divisions like this does not have a sufficient capacity to serve all users; instead, several parallel elevators forming a group are needed in the same zone. A typical group consists of eight elevators serving the same zone, which may comprise e.g. floors 31-15. Often an elevator group like this is needed for each zone, for example for a mid-zone to serve floors 16-30 and a top zone to serve floors 31-45. The problem is that, in the case of this example, 24 elevator shafts are required, each of which extends from the ground floor upwards although only the eight elevators in the lowest group serve the fifteen lowest floors. The elevators serving the intermediate and top zones do not stop at the lower floors, so the lobby space and particularly the shaft space needed for them constitute expensive unused space for the owner of the building. The unused lobby spaces can be utilized e.g. as storage spaces or for lavatories on different floors, but the corresponding shaft space cannot be utilized in any way.
2. Description of Related Art
U.S. Pat. No. 5,419,414 represents a prior-art solution for an elevator arrangement in tall buildings. In this solution, three elevator cars are placed one over the other in the same shaft so that each car is moved separately by means of an elevator machine mounted above each common elevator shaft. Thus, a separate machine is provided for each elevator car, and the elevator ropes run from the machines to the elevator cars in a interlapping manner so that the ropes going to the lowest car pass by the two higher cars and the ropes going to the intermediate car pass by the uppermost car. The cars can be moved in relation to each other on at least four different operating principles. According to a first principle, each car always moves in its own shaft section and never enters the zone of another car. According to another principle, each car can serve all floors, but only one car can be moving at a time. According to a third principle, the cars can move simultaneously in different zones, but only in one direction at a time. Finally, according to a fourth operating principle, the cars can move simultaneously in different directions provided that safety is guaranteed. For example, when the two lower cars are going downwards, the highest car can move upwards. The proposed elevator system is very complicated and it is obvious that such a system involves the problem of how to construct a sufficiently simple and safe control system. Even if the control system were ever so safe, the system may still get out of order, in which case a collision between two cars is possible.
U.S. Pat. No. 6,273,217 also discloses an elevator solution in which more than one elevator cars are travel in the same elevator shaft. The solution presented in the patent is focused on preventing a possible collision of two elevator cars by means of a program. If a risk of collision appears, one of the elevator cars is moved away to give way to the other one. The problem in this case, too, is exactly a risk of collision, because there is always the possibility that, if a program malfunction or error occurs, two elevator cars running towards each other in the same shaft will collide.